Showing papers in "Journal of The Society of Materials Science, Japan in 1963"

Viscoelastic Behavior of Polymer Blends and Its Comparison with Model Experiments

Abstract: Methods for evaluation of viscoelastic behavior of blends of amorphous polymers from those of component polymers were investigated by model experiments and the limitations of the methods were examined.It is possible in principle to calculate the properties of polymer blends from those of component polymers for the system consisting of two separate phases. In order to establish the description method for this system, model specimens were prepared by bonding together the films of component polymers of known size, and dynamic modulus E' and loss modulus E" were measured at 138c/s over a temperature range from -170°C to 120°C. The film of polyvinyl chloride (PVC) and that of nitrile-butadiene rubber (NBR) were used as materials of the model specimens. The results of measurements were compared with the values calculated from dynamic properties of component polymers.Close agreement was obtained between the observed values of E' and E" of various types of model specimens and the values calculated by the equation, in which the volume fraction and the construction form were taken into consideration.As an example of the two phase system, Cycolac H of Marbon Chem. Co. was studied. Its temperature dispersion curve resembles closely to that of model specimen, which was constructed by putting the rubber phase (NBR) into the plastic phase (PVC). The location of the higher temperature dispersion of Cycolac H, 115°C, accorded with that of the dispersion of a styrene-acrylonitrile copolymer separately measured. The lower temperature dispersion at -185°C was found to correspond to that of polybutadiene. The dispersion curves of Cycolac H were successfully calculated by employing those of the component polymers based upon the two phase simple model.As an example of molecularly mixed system, the measurements were performed on the specimens prepared from PVC and NBR of various compositions by the solvent casting method with tetrahydrofuran. Of all the compositions, only one main absorption was found at the temperature region between the absorptions of PVC and NBR. The shape of absorption becomes most broad at the intermediate compositions. This broadness is considered to be due to the microheterogeneity in segmental size, corresponding to the varieties of segmental environment. The general expression for this case was presented.The shape of temperature dispersion curve for the partially miscible system showed an intermediate form between those of the typical two phase system and the molecularly mixed system. The behavior of blends of a styrene-acrylonitrile copolymer and NBR belongs to this type. Observed values for this system were compared with the values calculated on the basis of the typical two phase system of the same compositions. Definite deviations from calculated values were found, which were duly ascribed to the portion of molecularly mixed phase. Broadening of absorptions of both rubber and plastic phases could not be interpreted from the typical two phase model, but only from the consideration of the effect of molecularly mixing.This circumstances were ascertained by the behavior of the model specimen specifically prepared for this purpose.

On the Volume Changes of Normally-Consolidated Clays

Abstract: Changes in volume of soils are a function of changes both in normal stresses and shearing stresses. Development of mathematical expressions for the change in volume would be of aid for the understanding of the failure criteria for clays and would permit more reliable estimates for the settlement of structures founded on massive clay deposits.This paper describes an investigation of the stress-volume change characteristics of a normally-consolidated clay. The test procedure was similar to that in the case of drained compression test, except that the loading was arranged so that the mean principal effective stresses might be maintained constant throughout the test.The nomenclature used in this paper is as follows: C: coefficient of compressibility. D: coefficient of dilatancy. V0: initial volume corresponding to σ0'. ΔV: total volume change. ΔVc: change in volume due to the change in mean principal stress. ΔVd: change in volume due to the change in shearing stress. σ1' σ3': principal effective stress. σm': mean principal effective stress. σ0': pre-consolidation pressure. σc: critical stress, below which dilatancy is zero. σm'-const.-test: drained compression test in which the mean principal effective stress is maintained constant.The analysis of the test data shows that the volume change behaviour can be adequately described by the following conclusions:1) The volume of normally-consolidated clays decreases when the mean principal effective stress is increased, and vice versa. The virgin branch of a semi-logarithmic plot of the consolidation diagram is usually straight (Fig. 1) and can be expressed by the equationΔVc/V0=C·logσm'/σ0'2) The volume decreases when normally-consolidated clays are subjected to an increase in shearing stress. Fig. 6 shows that the volume change during a σm'-const.-test ΔVd/(V0-ΔVc) is a unique function of (σ1-σ3)/σm' and correlations between them can be established.ΔVd/(V0-ΔVc)=D{(σ1-σ3)-σc/σm'}3) The total volume change ΔV of normally-consolidated clays is ΔV=ΔVc+ΔVd, then ΔV is given by the expressionΔV/V0=C·logσm'/σ0'+D(1-C·logσm'/σ0'){(σ1-σ3)-σc/σm'}

Investigation on the High Frequency Fatigue (The 1st Report)

Abstract: To investigate the influence of loading frequency in high speed fatigue of metals, a pneumatic machine for fatigue testing at frequencies ranging from 150 to 2000 cycles per second has been designed.Method for excitation used is an air nozzle system of so-called flutter type, in which the specimen vibrates in a direction transverse to the air stream, and it does not require complicated control system to maintain resonant condition.Specimens are thin reeds of 1.2mm in thickness and 4 or 5mm in width at the test section, and are vibrated in the fundamental mode of cantilever beam.Strain amplitude of the loaded specimen was measured by electrical resistance strain meter, and certain considerations about measurement were made with respect to gauge length, thickness of gauge base and temperature increase during test.Cyclic strain fatigue tests were made at room temperature on an annealed 0.23% carbon steel, and it was found that the endurance limit increased with increasing test speed in this range of frequencies.

Some Anisotropic Properties on the Strength of the plywood

Abstract: The calculation formulae ralating the stress in bending of the laminated wood-beam were checked by tests and verified their appricability to the plywood.The anisotropic properties of strength of the plywood can be represented by the ratios of AE=E90/E0, BE=EB90/EB0 and NR=R90/R0 where E0, EB0 and R0 denote respectively the elastic moduli in edgewise tension or compression, the elastic moduli in bending and modulus of rupture in bending of plywood parallel to the face grain, and E90, EB90 and R90 denote those values of plywood perpendicular to the face grain. These values in the cases of 3-ply, 5-ply and 7-ply plywood of LAUAN which are constructed from single species and have symmetetrical construction to their core are evaluated by the computed results using the basic strength of veneer, and the anisotropic properties of them are discussed.

The Influence of Non-metallic Inclusions on the Fatigue Strength and the Statistical Nature of Steel

Abstract: Three series of specimens were specially prepared so that they may contain various degrees of MnS non-metallic inclusions, other parameters being kept constant especially the amount of manganese in solution as much as possible. Fatigue tests were carried out with a rotating bending fatigue machine.The results obtained are as follows:(1) The definite relationship could not be recognized between the inclusion ratings and the statistical nature of fatigue life of steel, which is in accordance with the previous work by one of the present authors, but contrary to the result by Epremian and Mehl.(2) The ferrite grain size is a predominant metallurgical factor in the statistical nature of fatigue fructure of steel.(3) For the same stress amplitude, the scatter of fatigue life increases and the probability of fructure decreases with the decrease of grain size.(4) For the equivalent stress amplitude, the scatter of fatigue life appears not to be affected by inclusion ratings and ferrite grain size.(5) The longitudinal fatigue strength of carbon steel is not so much affected by the content of MnS as inclusions. The effect by ferrite grain size or other statistical parameters may also be large.

The Theoretical Research on the Stress Relaxation of Clay

Abstract: Recently, with development of soil engineering, when we stand on a view-point that the soil is also one of the engineering materials such as the high polymer or metal, and wish to explain unificatively the complicated mechanical behaviour of soils, it is methodologically necessary that we must consider an introduction of thermo-dynamics and statistical mechanics based on the molecular theoretical investigation.In this case, however, we cannot avoid facing a difficulty which is due to that the deformations of soils are irreversible in general, because the thermo-dynamical analysis is confined to considerations of reversible process of deformation only.Then, in order to overcome the above difficulty, the authors have established several assumptions as follows:(1) The authors have adopted a network structure of“card-house”presented by T. K. TAN1) for the skeletal structure of clay. However, we cannot mathematically express a formal distribution of the skeletal structure merely by this network structure. Therefore, a pattern showed in Fig. 2(a) was presented by the authors anew, which was a cross section of the clay network structure. In Fig. 2(b), a broken line turned at random was called“imaginary chain”of the clay network by the authors, further the mutual contact between the clay particles (i.e., the turning point of the imaginary chain) was denominated“unit mechanism of deformation”. The bonding force at this contact point, of course may be due to Coulomb attraction force between the positively charged edges and negatively charged flat sides of the clay particles, van der Waals forces, bonding by cations, and dipole hydrogen bridges.(2) For the deformation process, we have assumed that a micro elastic deformation may occur at the instant of loading, and a retarded deformation that is due to slipping of the clay particles follows on the instantaneous elastic deformation. The macro plastic deformation consists of these two deformations. The micro irreversible deformation at the contact point occurs only when the stress component acted to the unit mechanism of deformation becomes greater than the bonding energy of the contact point.(3) For a thermo-dynamical expression of the micro reversible deformation process of the clay, we have assumed that the external force is composed of the energy elasticity and the entropy elasticity, and the former is proportional to the latter.By the above hypotheses, the authors have accomplished the introduction of thermo-dynamics and statistical mechanics to soil mechanics. As a result of the theoretical investigation, the authors have obtained a unificative equation (12) that is of the same type as Maxwell's equation. However, by the simple Maxwell's equation, it is not yet enough to explain the complicated rheological properties of clay, and so the authors introduce the structural viscosity of clay by applying Eyring's viscosity theory to the double water layer of clay particles. Consequently we have been able to explain molecular theoretically the rheological behaviour of clay.

Creep of Gelatin

Abstract: Creep of gelatin-water system was studied covering a wide range of concentration at several different temperatures. The sample studied is unfractionated and photographically inert alkali-processed hide gelatin with isoelectric point of pH4.8. Creep at higher concentrations was measured with automatically extension-recording apparatus or travelling microscope at definite humidities and definite temperatures, and that at lower concentrations with special gel elastometer. The strain values were limited to be less than 1%.The result of the measurements suggests the existence of three concentration regions showing deformation with different mechanisms in mechanical behavior.First, glassy state above 85% in concentration at 20°C. It is reasonable to surmise that water molecules are present at hydration centers of the amorphous region of gelatin. Creep compliance curves at various concentrations are superimposed on each other, and compose a smooth curve through usual horizontal shift along time axis.Second, dispersion region. The concentration range at 20°C is from about 40 to 83%. Young's modules and creep compliance depend remarkably on concentration, and the dependency seems not very simple. The upward shift of creep compliance curves for gelatin at pH 4.8 maintaining its shape was found when concentration decreased, therefore, the composite curve was obtained through vertical shift along creep compliance logJ axis. Horizontal shift as well as vertical shift was necessary to superimpose creep compliance curves at pH6.5, but the former reducing factors were smaller than the latter one. Increasing amount of water saturates all available hydration centers in amorphous region of gelatin, then induces disturbance of crystallites, and then is supposed to decrease the degree of crystallinity remarkably. The large vertical shift above-mentioned is considered to relate with crystallinity changes according to the recent research on synthetic, crystalline polymers. The crystallites in this region may be micelle-like.Third, the square law region. Elasticity modulus of gelatin gel is proportional to the square of gelatin concentration up to about 30% but from that to 40% the modulus is less than the value predicted from the square law. To superimpose the creep compliance curves, vertical shift along logJ axis was necessary. Here, the gel is essentially rubber-like, and the cross-linkages may be formed between two chain segments, caused by secondary bonds. Since the cross-linkages are evidently dissociated by decreasing gelatin concentration or arising temperature, vertical superposition may become possible.In conclusion, the viscoelastic properties of gelatin not in glassy state are characterized by vertical shift of the curves denoting them concerning with concentration or temperature, and horizontal reducing factor log b is null or nearly null, otherwise not null but always smaller than vertical reducing factor. The different mechanisms of viscoelastic deformation in three regions in concentration above-mentioned result from the structural difference of gelatin.

Dynamic Viscoelasticity of Concentrated Polymer Solutions in Steady Shear

Abstract: Dynamic Viscoelasticity of Concentrated Polymer Solutions in Steady Shear by Kunihiro OSAKI, Mikio TAMURA, (Department of Industrial Chemistry, Kyoto University, Kyoto) Michio KURATA and Tadao KOTAKA (Institute for Chemical Research, Kyoto University, Kyoto) Dynamic viscoelasticity of concentrated polymer solutions in steady shear is studied by means of a coaxial cylinder type rheometer, of which outer cylinder can be given three types of motion, namely sinusoidal (rotational) oscillation, stationary rotation and oscillatory rotation. Oscillatory and stationary parts of inner cylinder motion are separately recorded by electric devices. It was found experimentally that synthesis of inner-and outer-cylinder oscillations gave an ideal Lissajous pattern irrespective of magnitude of steady shear superimposed, and that the dynamic modulus Gγ* under a constant rate of shear γ can be determined as function of angular frequency ω by 1) using the Markovitz equation for the motion of linear viscoelastic materials in an annular space.

The Influence of the Specimen Surface on the Measurement of Residual Stress by X-Rays

Abstract: It is a recent remarkable tendency that the method of X-ray stress measurement by means of X-rays has come to be widely utilized in many laboratories. It is also a fact, however, that some experimenters concerned with this measurement have still some doubts about its accuracy.The results of the experiments carried out in our laboratory, as was reported last year in the special issue of this society pertaining to the measurement of stress by X-rays, showed a high accuracy in the measurement. This high accuracy is considered to have been established as a result of the confirmation that the condition of the specimen surface has an important effect on the accuracy in the measurement of stress by X-rays, which was obtained through a number of investigations in our laboratory.Some literature concerning the measurement of stress by X-rays, however, treat the influence of the surface condition lightly. Accordingly, in order to make this point clear, experiments were carried out using the specimens with various surface conditions. As a result, it was found that the stress measured in the specimens with fine surfaces is in good agreement with the load stress, while that of the specimens with rough surfaces show discrepancies. Besides, as regards the residual stress, the measured values of the specimens with fine surfaces were found to be larger than those of the specimens with rough surfaces. The difference between both the measured values became larger as residual stress increased.The reason why the measured values show differences according to the conditions of the specimen surface might be ascribed to the circumstance that they may have some connection with the depth of penetration of X-rays. In case the specimen surface is rough, the real stress value may not be obtained for the shallow penetration of X-rays, because the stress in the projected area is relieved. Therefore, the specimen surface must always be flat and smooth However most specimens in our use are far from satisfying this condition. Consequently, polishing method is used to obtain a smooth surface, but in the course of polishing stress is introduced, resulting in the shift of the true stress value. In order to eliminate this stress in processing, etching methods by means of chemicals such as hydrochloric or nitric acid have been employed so far. Experiments, however, have shown no good results on the chemically etched surfaces.In our laboratory, therefore, taking the flatness of the specimen surface after the removal of stress in processing into consideration, electrolytic polishing method has been adopted, as was reported in the special issue of this society concerning the measurement of stress by X-rays. Besides, an electrolytic polishing apparatus was manufactured which is capable of eliminating the stress in processing in any specimen in a short time and which is used in our laboratory.This report contains the results obtained for the case in which Cr-Kα rays were employed as characteristic X-rays. If Co-Kα rays with a different penetration depth from that of Cr-Kα rays were used, the results might be somewhat different from this report. But it remains a common requirement that the specimen surface should be flat and smooth. As regards the relation between the roughness of the specimen surface Co-Kα rays, the authors will further their researches and await another opportuuity to report the result.

Elastic Hysteresis Property of Several Steels under Fatigue Load

Abstract: The authors have previously reported on the mirror extensometer which magnified the longitudinal elongation and the contraction of the specimen under axial fatigue load as much as 2000 times, and on some of the experimental results obtained of two kinds of steel.In this paper, similar experiments were made on five kinds of carbon steel. The strain occurred on each specimen under completely reversed axial load was measured through the test. The plastic strain, by which we mean half the width of a hysteresis loop on the stress-strain diagram, was obtained from a simple calculation.There was ovserved a difference between the behaviour of plastic strain of the low carbon steels and that of the high carbon steels. Howevever, the variation of the plastic strain was moderate and converged to some final value. One exception was the case of 0.25% carbon steel. This steel showed a quite different and complicated behaviour of the plastic strain that offered us a subject of more detailed investigation in future. For the other steels, there exists a linear relationship between the plastic strain and the number of stress cycles to failure when plotted on a log-log paper. A similar relationship was found when the hysteresis energy was plotted instead of the plastic strain. Some discussions were also made on the stress-strain curves under fatigue load.

Effects of Emulsifiers on Flow Behavior of Emulsion

Abstract: (1) Flow properties of emulsions containing from 10 to 60vol. % of liquid-paraffin in water, stabilized with SDS or Tween 60, have been investigated using Maron and Belner's capillary viscometer at 32°C.Viscosities of SDS system do not depend on the rate of shear at dispersion concentrations below 40vol. %. Tween 60 system shows non-Newtonian flow over the range of dispersion concentrations at relatively low rate of shear. At higher shear rate, flow of the Tween 60 system tends to show Newtonian behavior and the values of the relative viscosities of the system agree with those of SDS system at the same dispersion concentrations.These differences in flow behavior of the two systems may be attributed to the difference in the dispersion state, which is remarkably influenced by the nature of the surface layer on the dispersed particle.(2) Flow properties of surface active agent (emulsifier) aqueous solutions containing n-octanol or n-hexane have been studied at 32°C.In n-octanol system, values of viscosity increase with the increasing amount of solubilized n-octanol and pass through a maximum value in the neighborhood of the concentration of the limit of solubilization and decrease again with the further addition of n-octanol. In n-hexane system, the values of viscosity increase with the increasing amount of n-hexane in a fairly normal way.These differences in flow behavior of the two system may be attributed to the difference in polarity between n-octanol (polar liquid) and n-hexane (non-polar liquid).

The Steady Flow of a Viscous Fluid through a Conical Nozzle

Abstract: The purpose of this paper is to present a theory of the steady flow of Newtonian liquid through a conical nozzle. The equation of motion of viscous liquid has been treated on the following assumptions: i) the liquid is incompressible; ii) the motion of liquid is not turbulent; iii) the motion is steady; iv) no body force acts on the liquid; v) the motion has an axial symmetry; vi) there is no slip at the wall; vii) the stream lines are the straight lines passing through the vertex of the cone, that is, the end effect is neglected; viii) the motion is so slow that the inertia term can be neglected.We have taken a spherical coordinate system r, θ, and φ whose origin is at the vertex of the cone. Then the velocity is given byvr=3A(cos2θ-cos2α)/4r2, where α is the semi-angle of the cone, and A is a constant. The expression for the pressure is obtained as follows:p=p0+3/2Aη[cos2θ+1/3/r3-cos2α+1/3/r13], where η is the coefficient of viscosity, and p0 the atmospheric pressure. Thus the average pressure gradient taken over the spherical surface of radius r is given by(∂p/∂r)=-3/2Aη/r4(2+cosα+cos2α).On the other hand, the volume of flow in unit time is given byQ=-πA(1-cosα)2(1+2cosα).Eliminating A from the above two equations, we getQ=π/8R4/η(∂p/∂r)F(α), where R is equal to rα, and F(α) is given byF(α)=16/3(1-cosα)2(1+2cosα)/α4(2+cosα+cos2α).Since limα→0F(α)=1, the above equation may be reduced to Poiseuille's equation for a tube of uniform cross section.From the expression for the velocity vr we can calculate stress components of the fluid. Especially, the tangential stress σrθ is given byσrθ=-3/2Aηsin2θ/r3.For a given value of r, σrθ varies as sinθ does in contrast with the case of a tube of uniform cross section where tangential stress decreases linearly from a maximum to zero with decreasing distance from the axis of the tube.

18-8ステンレス鋼の高温ねじりクリープ強度に関する研究 (第4報)

Abstract: In the last paper, authors reported that the torsional working temperature has a remarkable influence on the torsional creep limit of a plain 18-8 stainless steel. Through the present investigation, measurement of torsional creep limit of a 18-8 Cb Stainless steel bar (5mmφ×50mm) austenized and twisted to a degree of 0.128π/cm or 0.256π/cm was made at 500 and 600°C, and then hardness and micrographic testing and X-ray analysis were carried out. These results obtained are summalized as follows:Torsional creep limit of a 18-8 Cb stainless steel is not so much affected by the torsional working temperature of -60∼800°C as in case of the creep limit of plain 18-8 stainless steel.In this 18-8 Cb stainless steel, it was found that the effects of torsional working temperature on the difference of the hardness before and after creep testing and also on the precipitation mode of Cb-carbide (CbC) were small.

On the Bending Stress and the Contact Pressure of a Wire Rope on a Cast Iron Roller

Abstract: The bending stress of wire rope and the contact pressure between the wire rope and the cast iron roller have an important effect upon the durability of the wire rope. There have, however, been few studies made on the contact pressure beyond a series of studies by Th. Wyss.Furthermore, Th. Wyss' studies seem to have some doubtful points, so the authors developed some experimental investigation on the contact pressure of a wire rope in order to solve these problems and tried to make the matter clear theoretically by attempting to extend Hertz's stress theory into the plastic region.We have obtained some satisfactory results on the contact pressure, and succeeded in inducling a practical formula for calculating the bending stress based on the experiment;1) The maximum bending stress of a wire rope on the cast iron roller can be estimated by the fomulaσb=(1∼1.2)EbQd/4√EIS2) The contact pressure between the wire rope and the cast iron roller can be calculated by using P/dr2-Aμνdr2 curve, and the maximum value of the contact pressure can properly be taken as 180kg/mm2.

X-Ray Investigation of the Residual Stress of Metallic Materials

Abstract: The X-ray method of stress measurement is taken as a unique method of non-destructive measurement of local stress. Recently the experimental technique and the theory of stress measurement by X-rays have been greatly improved. From the results of recent study, it is understood that the mechanically applied stress with in the elastic limit can be measured by X-rays with sufficient accuracy.In the case of measurement of residual stress by means of X-rays, however, there remains a question whether the stress measured by X-rays represents the macroscopic residual stress itself. Since the lattice spacing is taken as the gauge length for measurement of strain, it is plausible that the microscopic nature as well as the macroscopic nature are included in the value of the stress obtained. In the present study, experiments were carried out to find the influence of microscopic nature on the valuation of residual stress by X-rays using stretched plate specimens of carbon steels.Eight sorts of carbon steels with carbon content ranging between 0.14 and 1.00 percent were used as the material of the specimens. All the specimens were annealed after the forming. The plastic tensile strain of a quarter and a half of the strain at the maximum load in tensile test was given for every material, and residual stress measurement was made by X-rays and mechanical methods for the stretched specimens. It was intended to compare the distributions of residual stress determined by both these methods.As the X-ray diffraction apparatus, an automitic X-ray stress analyzer of the parallel beam type with the Geiger-Muller counter tube was used. The Cr-Kα radiation was employed, which gave diffraction from the (211) crystal planes of carbon steel. For the purpose of determining the distribution of residual stress by X-rays, a thin layer was successively removed on both the surfaces of the plate specimen, and the stress on the revealed surface was measured. On the other hand, the macroscopic residual stress was measured by the conventional mechanical method of successively removing of thin layers only on one side of the specimen.The obtained results are summarized as follows: -1) Compressive residual stress is observed in the surface layers of the stretched specimens, and its value seems to be independent of the stretched strains.2) The accuracy of the stress value by X-rays measured by the sin2ψ method is sufficiently reliable.3) The residual stress on the surface of the stretched specimens by X-rays shows non-uniformity from place to place of the surface. It is considered that the non-uniformity of stress value by X-rays must be taken into consideration in the comparison of the stress measured by X-rays with that measured by mechanical means.4) The compressive residual stress measured by the X-ray method increases with the increase of carbon contents both on the surface layers and at the core of the specimen. If the stress value by X-rays represents only the macroscopic residual stress, it must converge to zero at an infinitely small thickness after the successive removal of layers from both the surfaces. However, the experimental result shows the existence of compressive residual stress in such a case. Therefore, it is considered that the residual stress measured by X-rays in the stretched carbon steel includes the macroscopic residual stress caused by the surface effect and also the microscopic nature due to the plastic deformation, and the cause of the discrepancy between the X-rays and the macroscopic residual stress in the stretched carbon streel cannot be explained by the criterion of the phase stress (Gefugespannung) alone.

Rheology of Powder (II)

Abstract: In the previous paper we reported that the internal friction of powder is related to the variation of void during tapping or the powder constant of Nutting's equation. And it was seen that the shearing stress increases pulsatively with the increase of shearing displacement and saturates gradually.In this study we carried out determination of pulsative vibration of the shearing stress during flowing of powder by the use of modified Green's rotational cylindrical viscometer. The stress of inner cylinder in response to the shearing stress of powder due to the rotation of outer cylinder represented pulsative vibration at early period and got to the constant of amplitude at the later period of rotating time.From the results of the recording of pulsative flow patterns obtained employing various kinds of powder, it was found that the amplitude of vibration is related inverse proportionally to the cohesive property of powder.From the analysis of flow pattern could be derived two types of mechanism of flow properties, i.e. the random flowing of each particles and the flowing of the block of powder. Both types of flowing of particles are attributed to the variation of void during flowing.An empirical dependence of the mean torque on the duration of the experiment can be satisfactorily represented by the relation;|(T-T∞)/(T∞-T0)|=expKNwhere T is the mean torque at any time, T0 the torque at the initial time of the experiment and T∞ the equilibrium torque after long time. N is the number of rotation and K is a constant relating to the speed of rotation and depending on the packing rate of powder. Subsequently the above equation agree to Roller's equation which was obtained from the relation between the variation of density of powder due to tapping and the number of tapping.